Ultrasound

J. Taylor Whaley, MD The Abramson Cancer Center of the University of Pennsylvania Last Modified: December 1, 2014

An ultrasound (US) is a non-invasive radiology test that creates pictures of internal organs through the use of sound waves. It is also commonly referred to as sonography. USs were first designed to detect and track submarines during the early 20th century. The use of sonography in medicine began in the 1950s; however, as all computer technologies have dramatically evolved in the past few decades, so too have USs.

USs are most known for their use in obstetrics, primarily in pregnancy; however, US can also be used to look at organs in the abdomen (liver, kidney, gallbladder) as well as the heart and blood vessels (arteries and veins).

US is a tool, used in addition to history, physical exam, and labwork, to better diagnose medical problems. As with any radiology test, it is very important to understand that without talking to the patient and knowing the medical history, USs can be very difficult to interpret.

USs are relatively cheap and quick tests, and are widely available throughout the U.S. and many countries.

What is this test used for?

USs can be used to evaluate many parts of the body. USs are occasionally used in emergency situations, looking for blood in the abdomen, a blood clot in the leg or looking at the heart; however, the vast majority of USs are performed non-emergently and scheduled as an outpatient procedure.

USs are used throughout pregnancy to evaluate the growing fetus, inside the mother's uterus. USs can also be used to evaluate irregularities seen during a mammogram.

Similarly, USs can be used to evaluate patients for blood clots in the leg, also known as a deep vein thrombosis (DVT).

For patients with cancer, USs are often used to check for enlarged lymph nodes. USs can be used in the under arm or groin. When tumors are deep within the body, an US probe can be added onto an endoscopy or bronchoscopy tool so the doctor can check for enlarged lymph nodes within the GI track or the lungs. These are respectively known as endoscopic US (EUS) or endobronchial US (EBUS).

Finally, USs are frequently used to evaluate the prostate in men with concern for prostate cancer. Transrectal USs (meaning the US probe is inserted into the rectum to view the prostate gland) are generally used for prostate biopsies.

Some USs have the ability to evaluate blood flow.

How is this test performed?

An US can be performed as an inpatient or outpatient procedure. An US will focus on a specific part of the body.

An US is performed by a technician who will place a transducer, or probe, onto the skin. A gel is applied to the skin to allow the probe to make better contact with the skin. The probe produces sound waves that travel into the tissue and then reflect off tissues within the body and return to the probe.

The test is non-invasive and usually painless.

As the waves return to the probe, an attached computer interprets the pattern. The computer then transforms the pattern to create an image that can be interpreted by a radiologist.

Can anything be evaluated with an US? Actually no. This is because while US waves work well in parts of the body made up of tissue or water, US cannot transmit across bone or air. This is the major limitation of US.

A radiologist, who is a doctor specializing in looking at different types of images of patients, evaluates the US and generates a report; however, some USs can be evaluated without a radiologist. Two examples of this include pregnancy USs, which are interpreted by obstetricians, and heart USs (echocardiogram), which are interpreted by cardiologists.

US can be used in biopsies. This is because US produces real time images on the screen, the doctor can use these pictures to guide the needle during a biopsy.

Because US uses sound waves, there is no radiation involved.

The test generally only takes 15-30 minutes to complete, depending on the size and complexity of the area being evaluated.

How do I prepare for an US?

Typically, no preparation is needed for an US.

If the US is going to evaluate your gallbladder, you may be asked to fast for 4 hours prior to the test.

If the US will be placed rectally for a prostate biopsy, a colonoscopy-like prep is generally needed to clear the bowel of stool. If the scope will be inserted either endoscopically (through the mouth and esophagus) or bronchoscopically (into the lungs), you will be asked to fast to prepare for the sedation medications that will be used.

Picture of an US machine

How do I interpret the results of an US report?

The results of the test depend on which part of the body was imaged. Following the US, the images are processed by a computer and read by radiologist or other trained physician. The radiologist then generates a report for your doctor.

The report generally states the patient's name, date of birth, and indication (reason for the test) at the top of the report. Radiology reports follow a standard outline, regardless of where they are obtained. Radiologists report both normal and abnormal findings in a very systematic approach. In turn, some things mentioned in the report may be meaningless for your situation, but appear concerning to a layperson. For this reason, it is very important to discuss the results with your doctor.

If the US will be placed rectally for a prostate biopsy, a colonoscopy-like prep is generally needed to clear the bowel of stool. If the scope will be inserted either endoscopically (through the mouth and esophagus) or bronchoscopically (into the lungs), you will be asked to fast to prepare for the sedation medications that will be used.

The first paragraph typically includes the specific technical information involved in obtaining the scan (i.e. what the exam evaluated, etc).

The middle paragraphs generally begin the description of findings, both normal and abnormal. Because reports are generated for other medical professionals, the terminology is often medically oriented and can be difficult to interpret.

Following the detailed interpretation above, an impression generally follows. This is a summary of the findings, often generated to answer the question posed by the ordering physician.